In the related art, a technology for detecting a short to power, a short to ground, and disconnection has been proposed (see Patent Document 1 for instance). In this technology, a detection voltage based on a comparative voltage which is lower than a power supply voltage and is higher than a reference voltage (GND) and a voltage between a power supply and a reference voltage unit is generated.
Patent Document 1: Japanese Patent Application Publication No. 2013-108819A
There is a case of generating a comparative voltage clamped to a predetermined upper limit value on the basis of a constant voltage and generating a detection voltage, as a threshold value for abnormality detection, on the basis of a power supply voltage. Further, a voltage clamped to a predetermined upper limit value on the basis of a certain voltage is also referred to as a clamp voltage. In this case, there is a possibility that the comparative voltage and the detection voltage may vary depending on different voltages, respectively, causing the relation of the magnitudes of the comparative voltage and the detection voltage to be inversed. In other words, if the power supply voltage falls to about the above described upper limit value for any cause, the detection voltage varies depending on the power supply voltage, whereas the comparative voltage does not vary. Therefore, it is feared to erroneously detect occurrence of an abnormality.